Adding a gravel event mid-block: what an adaptive plan should change in the next 4 weeks

Why a gravel event is a durability target, not an FTP target

Gravel events are durability problems first, intensity problems second. BWR runs roughly 6 hours, SBT GRVL 100 about 5 to 7, Unbound 200 around 10 to 13. The gating physiology is fat-oxidation capacity, fuel tolerance, and time-on-bike — not the 20-minute power number that drives a road build.

The acute load math makes the point. A 6-hour mixed-terrain event at moderate average intensity books 250 to 400 TSS in a single ride. For a 10-hour-per-week amateur whose normal week runs 550 to 650 TSS total, one event day is 40 to 70 percent of a normal training week. The day is not the problem the build needs to solve. The problem is the rider arriving at hour four still able to produce useful power, still digesting carbohydrate, still holding position on rough surface — all of which sit downstream of the aerobic engine and the gut, not the threshold ceiling.

The physiology is well-mapped. San-Millán and Brooks' metabolic-flexibility work [San Millán & Brooks 2018] documented that elite endurance athletes oxidize fat at roughly double the rate of less-fit subjects at the same relative intensity, with peak fat-oxidation rates landing around 0.6 to 0.9 grams per minute in trained cyclists. Costa and Hoffman's ultra-endurance nutrition review [Costa & Hoffman 2019] is explicit that fueling tolerance — the ability to process 60 to 110 grams of carbohydrate per hour without GI failure — is itself a trained adaptation, not a given. A rider whose normal long ride is 2 hours has never asked the gut to process 600 grams of carbohydrate in one session. The event is the first time the system has been stressed at that load.

What changes in the next 4 weeks: long-ride absorption and fuel rehearsal

The weekend long ride is the lever. In a sweet-spot build it would have been a 2-hour endurance plus tempo session; for a gravel target it absorbs 30 to 50 percent of event duration with the rider fueling at race intake rates. Weekday quality compresses to one session; the second high-intensity slot converts to mid-length endurance.

The mechanism is specificity dosing. Issurin's block-periodization framework [Issurin 2010] separates accumulation work — voluminous low-intensity volume targeting mitochondrial biogenesis — from transmutation work targeting event-specific demands. A mid-block gravel target shifts the accumulation-to-transmutation balance toward accumulation, because the missing adaptation is time-on-bike capacity, not threshold power. Practically, the long ride scales to roughly 50, 60, 70, and 75 percent of event duration across the four-week run-in, with the last build long ride landing 10 to 14 days out so it remains absorbable into the taper. Two of those rides should include the surface and equipment combination the event will use — not for fitness, but to surface tire, hydration, and contact-point problems while there is still time to fix them.

Fueling is the other adaptation. Jeukendrup's personalized carbohydrate-intake review [Jeukendrup 2014] establishes the dose-response: roughly 60 grams per hour with single-source glucose, climbing to 90 grams per hour with multi-transportable glucose-fructose blends as event duration crosses 2.5 hours. Costa and Hoffman [Costa & Hoffman 2019] document that intakes above 60 grams per hour reliably produce GI symptoms in athletes who have not gut-trained the rate. The four-week run-in is where that training happens. The last two long rides should run at the planned race intake rate from the first hour, not just the last. A rider who has only ever taken 40 grams per hour and shows up at the start line planning to take 90 is rehearsing a bonk or a porta-john stop, not a race.

This is exactly what the broader pillar on adaptive cycling training plans means by life-adaptive. The plan absorbs the new target by reshaping the weekly shape — long ride up, second quality day down, weekly TSS within the original ramp band — instead of bolting extra rides on top of the existing schedule. A static plan handed the same event date typically does the latter and stacks the high-intensity work onto an already-loaded build, which is the textbook overtraining setup [Foster 1998].

What does not change: the polarized intensity distribution

The weekly intensity ratio holds. Roughly 80 percent of training time at low intensity, 20 percent at high intensity, very little tempo in between — the polarized pattern Seiler formalized [Seiler 2010] is not a road-versus-gravel question. Replacing the second weekly quality session with sweet-spot or tempo to feel more 'race-like' is the most common mistake.

The reasoning is direct. Seiler's polarized-training synthesis [Seiler 2010] is the most replicated finding in endurance research, and the principle is event-format-agnostic — the ratio of low to high intensity across the week is what produces the adaptation, not the specific surface. Substituting tempo for endurance to chase a 'gravel feel' produces a more monotonous week, a depressed low-intensity volume, and an aerobic engine that arrives at the event with less fat-oxidation capacity than it had before the substitution. Foster's monotony research [Foster 1998] flags exactly this drift as a leading behavioral predictor of illness and overtraining.

The single quality session that stays in the week should be the one that supports the event's demand. For most gravel events that means VO2max work — 4 to 6 minute intervals at 105 to 115 percent of FTP — because the surges that decide the race tend to land in that band, not at threshold. Issurin's block-periodization framework [Issurin 2010] supports keeping one concentrated high-intensity stimulus per microcycle rather than splitting it into two diluted sessions. The discipline is to resist the urge to make every weekday ride feel like preparation; most weekday rides during the run-in should be unambiguously easy.

The event itself is part of the plan: acute load and recovery

A 250 to 500 TSS event day is well outside any prescribed week's ramp band. The plan should treat the event as a planned overload and budget recovery accordingly — typically 7 to 14 days at substantially reduced load, with no quality work until the freshness signal recovers. Stacking a normal training week on top of the event is where most amateur post-event detraining starts.

Coggan and Allen's chronic-load framework [Allen et al. 2019] keeps weekly TSS climbing inside a roughly 4 to 7 TSS-per-day per-week safe ramp during build phases. A single 350 TSS event day, dropped into a week that already contained a 90-minute opener and a 60-minute easy spin, lands the week 40 to 60 percent over its acute-load target — well above the acute:chronic ratios associated with elevated illness and soft-tissue risk in the broader monitoring literature [Foster 1998]. Treating the event as 'just one ride' and resuming normal load Monday is the operational error. The week containing the event should be planned as the deload, not the week after it.

Practically, the post-event seven days run easy and short — zone 2 only, 50 to 60 percent of normal weekly TSS, no intervals. Returning to load while still recovering from a 6 to 12 hour event with high carbohydrate intake, sleep disruption, and contact-point trauma is the textbook non-functional overreaching trigger — the same high-load high-monotony pattern Foster's data [Foster 1998] identified in his 25-athlete cohort. The macro arc the plan was running before the event resumes in week two post-event, anchored to the new chronic-load number, not the pre-event one.

Quick answers

Sources cited in this guide

1. 01
   San Millán & Brooks 2018. Assessment of Metabolic Flexibility by Means of Measuring Blood Lactate Fat and Carbohydrate Oxidation Responses to Exercise in Professional Endurance Athletes and Less-Fit Individuals. Sports Medicine.
2. 02
   Jeukendrup 2014. A Step Towards Personalized Sports Nutrition: Carbohydrate Intake During Exercise. Sports Medicine.
3. 03
   Costa & Hoffman 2019. Considerations for ultra-endurance activities: part 1 — nutrition. Research in Sports Medicine.
4. 04
   Issurin 2010. New horizons for the methodology and physiology of training periodization. Sports Medicine.
5. 05
   Seiler 2010. What is best practice for training intensity and duration distribution in endurance athletes?. International Journal of Sports Physiology and Performance.
6. 06
   Foster 1998. Monitoring training in athletes with reference to overtraining syndrome. Medicine & Science in Sports & Exercise.
7. 07
   Allen et al. 2019. Training and Racing with a Power Meter (3rd ed.). VeloPress.

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